A study of the effect of growth regulators and time of plantlet harvest on the in vitro multiplication rate of hardy and hybrid tea roses

The effect of benzyladenine (BA) (0, 0.5, 2.5, 5 and 10 ppm), naphthaleneacetic acid (NAA) (0,0.005,0.01,0.1 and 1 ppm) and time of proliferation (six, eight and ten weeks) on the optimum multiplication conditions for four Rosa hybrida cvs Champlain, John Franklin, John Paul II and Landora were studied. BA and NAA both had a significant effect on the proportion of viable plantlets and on multiplication rates while low or high concentrations of these growth regulators in the medium generally caused a reduction of plant material. The optimum multiplication rate also varied with cultivar and time. Concentrations of NAA above 0.1 ppm decreased the multiplication rate significantly for two of the cultivars. There was no consistent response between multiplication rates and cultivars to concentrations of B A, NAA or even the time of culture, and it is therefore recommended that each of these variates be determined for each cultivar to obtain optimum plantlet yield.     

Effect of Single and Recurrent Gamma Irradiation on in vitro Shoot Cultures of Banana

ABSTRACT

Multiple shoot cultures of three banana cultivars belonging to AAA and AAB genomic groups (Basari, Chakkarakela and Rasthali) were irradiated with gamma rays. The percentage of individual shoot survival declined with increase in irradiation dose indicating an inverse relationship between the two parameters. Lethal dose of 50% was found to be 30Gy. Lower doses (10, 20Gy) enhanced shoot multiplication ratio, which however decreased with increased dosage. AAB cultivars appeared to be more sensitive as compared to AAA cultivars. The multiple shoots were also subjected to recurrent mutagenesis at an interval of 15 days. The percent (%) survival was found to decrease after each irradiation treatment, whereas multiplication ratio was found to be enhanced after third irradiation in Basrai. Individual shoots derived after different irradiation experiments were rooted and the plantlets were hardened in the green house. Among these, few showed morphological variations such as thick shiny dark green colored leaves, ovate leaves and a dwarf with a rosette of leaves in AAB cultivar, Rasthali. This is the first report on the effect of recurrent gamma irradiation on in vitro shoot cultures of banana.     

Corm induction and multiplication of Amorphophallus albus in vitro

Summary

Amorphophallus albus, belonging to the family Araceae, has attracted widespread attention due to its considerable economic and medicinal importance. The natural propagation coefficient of A. albus is very low, which limits application of this crop. In vitro corms can be used for propagation of A. albus and have been proved to be superior over in vitro plantlets. To optimise procedures for in vitro corm production and multiplication, the effects of phytohormones, sucrose concentrations and incubation conditions with desirable phytohormone combinations for callus induction, corm formation and corm growth of A. albus were investigated. The results showed that calli were induced at high frequency from petiole segments on Murashige and Skoog medium supplemented with 1.0 mg l^–1 naphthaleneacetic acid (NAA) and 1.0 mg l^–1 6-benzyladenine (BA). Compact nodular calli were desirable for corm formation, and optimum corm formation was obtained in the presence of 0.5 mg l^–1 NAA and 2.0 mg l^–1 BA. With this auxin and cytokinin combination, an increase in sucrose concentration from 2% to 6% (w/v) significantly increased the corm formation rate and favoured corm growth, but negative effects occurred at higher sucrose concentrations. By incubating over a range of temperatures from 19°C – 28°C, 22°C produced the largest numbers of corms and highest mean fresh weight of each corm. Short-day (8 h) or long-day (16 h) photoperiods did not affect corm formation and growth significantly, except that corm weight fell under long-day conditions. The multiplication rate of in vitro corms was enhanced by apical meristem wounding. It was possible to store in vitro produced corms at 4°C for as long as 90 d to overcome apical dormancy and accelerate sprouting after planting into soil. This work has established an efficient protocol for multiplication of A. albus through an in vitro corm system.     

Effects of growth regulators and activated charcoal on in vitro bulblet multiplication and growth in Galanthus nivalis ‘Flore Pleno’

Summary

The in vitro multiplication of Galanthus nivalis ‘Flore Pleno’ bulblet clumps was evaluated through three 16-week sub-culture passages on media supplemented with either 1.0 mg l^–1 6-benzylaminopurine (BA) and 0.1 mg l^–1 naphthaleneacetic acid [NAA; the plant growth regulator (PGR) control], 0.5 mg l^–1 BA and 0.05 mg l^–1 NAA (PGR/2), or 0.1 mg l^–1 BA and 0.01 mg l^–1 NAA (PGR/10). At the end of the second sub-culture passage, clumps of bulblets from each of the three PGR treatments were also transferred to conditions to promote bulblet growth (G medium without PGRs) supplemented with 60 g l^–1 sucrose and 5 g l^–1 activated charcoal (AC). Lowering the PGR concentration during the initial multiplication phase reduced bulblet multiplication and overall culture growth, but did not influence bulblet size, as indicated by the diameter of the largest bulblet. Lowering the PGR concentration during the multiplication phase also reduced the multiplication of bulblets, overall tissue fresh weight, and the production of roots in tissues transferred to bulblet growth conditions. The reduced growth of tissues previously multiplied on PGR/10 medium was not, however, reflected in the growth of individual bulblets, since these were not significantly smaller than bulblets initially multiplied at the higher PGR concentrations. Bulblet sprouting and root growth on the bulblet growth medium were unaffected by prior PGR status in the multiplication phase. The results are discussed in terms of the mode of action of AC on the promotion of bulblet growth.     

Comparative studies on nectar from two self-fertile and two self-sterile cultivars of quince (Cydonia oblonga Mill.) and their attractiveness to honeybees

Summary

Cross-pollination is of primary importance for quince (Cydonia oblonga), whose flowers reward pollinators with pollen and nectar. Characteristics of the nectar from two self-fertile (SF) and two self-sterile (SS) cultivars of quince were compared in a 3-year study, in order to establish if the two fertility groups differed from each other in terms of nectar production and/or insect attraction. The volume of nectar secreted per flower per day was measured using calibrated capillaries. The concentrations of nectar sugars were determined using a hand-held refractometer. The composition of nectar sugars was analysed using thin layer chromatography and densitometry. The quantity and quality of the nectar varied between years, cultivars, and fertility types. The volumes of nectar ranged from 0.40 – 5.30 µl flower^–1 d^–1 over the 3 years. The concentrations of sugars in the nectar produced flower^–1 d^–1 averaged ≥ 20% (w/w) in all cultivars, and ranged from 21.80 – 35.60% (w/w) over the 3 years. Significantly lower volumes of nectar were measured in the SF cultivars than in the SS cultivars in both years of the study. However, the concentrations of sugars in the nectar were not significantly lower in the SF group. The total sugar content of nectar varied between 160.59 – 347.65 mg ml^–1. The main sugar component in the nectar was sucrose, followed by glucose and fructose. Differences in the composition of nectar sugars could not be correlated with the two fertility groups. Our data showed that, although certain properties of their nectar make SS cultivars more attractive to honeybees than SF cultivars, members of the latter group can also attract sufficient numbers of bees to carry out cross-pollination, which is beneficial to both fertility types of C. oblonga.     

Development of a medium for in vitro culture of Galanthus species based on the mineral composition of bulbs

Summary

To optimise conditions for micropropagating Galanthus species, a basal medium (G) was developed based on mineral analyses of G. nivalis, G. nivalis ‘Flore Pleno’ and G. elwesii bulbs. Compared with Murashige and Skoog (MS) medium, the main features of G medium were increased concentrations of Cu ( 30.4), P ( 3.6), Ca ( 1.9), Mg ( 1.3) and S ( 1.2) and reduced levels of Mn ( 0.07), Zn ( 0.59) and K ( 0.65). The efficacy of G medium in supporting bulblet initiation on bulb chip explants, bulblet multiplication (on media supplemented with 30 g l^–1 sucrose, 1.0 mg l^–1 6-benzylaminopurine and 0.1 mg l^–1 naphthalene acetic acid), and bulblet growth (on plant growth regulator-free media with 60 g l^–1 sucrose and 5 g l^–1 activated charcoal) was compared with MS medium over a range of dilutions (full-, ¹?2-, ¹?4-, and ¹?8-strength). Bulblet initiation was superior on G medium for G. nivalis and G. nivalis ‘Flore Pleno’, but inferior for G. elwesii. The choice of basal medium did not influence bulblet multiplication, although multiplication was reduced on both media diluted to ¹?8-strength. G medium supported bulblet growth and rooting better than MS medium, while dilution of either medium reduced bulblet growth and rooting. Using G medium in place of MS medium during bulblet multiplication greatly reduced hyperhydration with G. elwesii, as did dilution of either of the basal media.     

Techniques for manipulation of the annual growth cycle in raspberry

Summary

Walnut (Juglans regia L.) leaves provide a source of healthy compounds, phenolics, which could be useful for the prevention of diseases in which free radicals are involved. In this study, walnut leaves from 14 different cultivars were studied for their total phenolics contents and anti-oxidant activities. Anti-oxidant activities were evaluated by measuring the scavenging activities of leaf extracts against 2,2-diphenyl-1-picrylhydrazyl (DPPH) radicals. The total phenolics contents of the cultivars ranged from 17.7 mg gallic acid equivalents (GAE) g^–1 FW to 39.6 mg GAE g^–1 FW. The highest scavenging activities were found in methanol extracts of walnut leaves. Total phenolics contents were highly correlated with anti-oxidant activity (R²= 0.94 – 0.92).     

Determining the S-genotypes of several sweet cherry cultivars based on PCR-RFLP analysis

Summary

Based on the cDNA sequences encoding sweet cherry self-incompatibility associated ribonucleases (S-RNases), a PCR-based S-allele typing system for sweet cherry cultivars has been recently developed. Using this technique, we determined S-genotypes of the three newly released Japanese cvs Kouka-Nishiki, Beni-Sayaka and Beni-Shuho and one British cv Merton Glory that was classified as a Universal Donor, which is able to be used as a pollen donor for all cultivars in pollen incompatibility groups I to XIII. Furthermore, we also determined the partial sequences of the S-RNase genes of ‘Rainier’ (S¹S⁴)‘ and ‘Sato-Nishiki (S³S⁶)’,which leads to the development of a more reliable S-allele identification method of PCR-RFLP for sweet cherry cultivars. Total DNA isolated from leaves of the four cultivars along with those from ten cultivars with known S-genotypes were PCR amplified with two sets of primers that were designed from DNA sequences encoding the signal peptide (Pru-T2) and two conserved domains (Pru-C2 and Pru-C4R) of sweet cherry S-RNases. By comparing the size of PCR products on agarose gel, the 5-genotypes of ‘Kouka-Nishiki’, ‘Beni-Sayaka’, ‘Beni-Shuho’ and ‘Merton Glory’ were suggested to be S¹S³, S¹S⁶, S⁴S⁶, and S⁴S⁶, respectively. Two of these three S-genotypes (S¹S⁶ and S⁴S⁶) were found for the first time. DNA sequencing of PCR products from S-alleles of ‘Rainier’ and ‘Sato-Nishiki’ revealed that Ban II, Nru I, Apa LI and Ava I sites, respectively, were unique in the S¹-, S³-, S⁴- and S⁶- sequences flanked by Pru-T2 and Pru-C4R primers. RFLP analysis of the PCR products using these enzymes confirmed that S¹-, S³-, S⁴- and S⁶-alleles of the four cultivars contained the respective restriction enzyme recognition sites.     

Rapid micropropagation of Psoralea corylifolia L. using nodal explants cultured in organic additive-supplemented medium

Summary

The influence of different growth regulators and additives on shoot multiplication from nodal explants of Psoralea corylifolia was investigated. Prolific shoot multiplication was achieved within 4 weeks of culture on Murashige and Skoog (MS) medium supplemented with 5 μM benzyladenine (BA), 5 μM ascorbic acid (AA), 100 mg l^–1 casein hydrolysate (CH) and 5% (v/v) coconut water (CW). Shoots elongated on half-strength MS basal medium devoid of inositol, but containing 5 μM 2-isopentenyladenine (2iP), 10 g l^–1 sucrose and 8 g l^–1 agar. Elongated shoots rooted on half-strength MS basal medium supplemented with 3 μM indole-3-butyric acid (IBA), 10 g l^–1 sucrose and 7 g l^–1 agar within 5 d of culture. The in vitro-raised plants were established successfully in 2:1:1 (v/v/v) garden soil:farmyard soil:sand, and maintained in a growth chamber with 100% survival. Acclimatised plants were transferred to a glasshouse and established successfully in the field. Flowers and fruits appeared after 4 months and resembled those on source plants. This system could be used for rapid commercial propagation of P. corylifolia for conservation strategies and to produce phytomedicines.     

Regeneration from in-vitro leaves of ‘Conference’ and other pear cultivars (Pyrus communis L.)

Summary

Regeneration of shoots from in-vitro grown leaf tissues of the pear cv. Conference was achieved at rates of up to 40%. The highest regeneration percentage was achieved using a phytohormone combination of benzylamino purine (5 mg 1^?1) and 1-naphthalene acetic acid (1.0 mg 1^?1) on a basal medium of Murashige and Skoog, to which had been added 200 mg I^?1 of the antibiotic cefotaxime. The percentage regeneration was reduced when a higher concentration of cefotaxime (400 mg 1^?1) was used. Cefotaxime had little beneficial effect on regeneration at a lower concentration of 1-naphthalene acetic acid (0.5 mg l^?1). Regenerated shoots were easily micropropagated, rooted and transplanted to soil. To date, the plants have a true-to-type phenotypic appearance. Regeneration was also achieved with other cultivars—‘Abbé Fetel’, ‘Doyenne d’Hiver’, ‘Doyenne du Comice’ and ‘Passé Crassane’—but percentage regeneration was lower and, apart from ‘Passé Crassane’, the regenerated shoots were weak and could not be subcultured.     

The Influence of Some Genetic and Environmental Factors on the Concentration of L-Ascorbic Acid in the Tomato Fruit

Summary

An efficient, reproducible protocol has been developed for in vitro multiplication of Sida cordifolia L. High-frequency, multiple shoots (90%) were obtained indirectly from nodal explants. Callus was induced when nodal explants were cultured on Murashige and Skoog (MS) medium supplemented with 0.5 mg l^–1 Kinetin (Kn). These nodal calli were then cultured in order to differentiate multiple shoots on MS medium supplemented with 0.5 mg l^–1 Kn plus 0.5 mg l^–1 naphthaleneacetic acid (NAA). Roots were induced from these multiple shoots following culture on MS medium supplemented with 0.8 mg l^–1 NAA for 4 weeks. Finally, these in vitro plantlets were hardened, acclimatised, and successfully transferred to the field.     

Factors affecting the quality and in vitro germination capacity of strawberry pollen

Summary

Poor pollen quality and germination capacity curtails early yield in strawberry. The aim of this study was to establish a reliable method for in vitro assessment of strawberry pollen germination ability and to investigate further the effects of photoperiod and gibberellin on pollen germination and quality. In the first part of the study, pollen from seven strawberry cultivars (Chandler, Selva, Tudla, Camarosa, Eris, Pajaro and Irvine) was collected and its germination capacity and incidence of deformed pollen grains assessed in vitro using the hanging-drop technique. Highest germination rates, in ‘Selva’, were observed in a nutrient medium of 10% sucrose. Addition of calcium nitrate to the medium decreased the germination percentages of all cultivars. There was no significant difference, on average, between the germination rate at 20° and 25°C. Genetic factors affected the incidence of deformed pollen grains significantly, with ‘Pajaro’ showing the highest percentage (76%). In the second part, groups of young strawberry plants, cultivar Seascape, grown either under natural early spring conditions or under long-day or short-day conditions were sprayed once with GA₃ at 0, 50, or 200 mg l^–1. Pollen germination and deformation and stamen length were assessed three months later. In plants of the first group, GA₃ at 50 mg l^–1 increased pollen germination and decreased the incidence of deformed pollen grains, while GA₃ at 200 mg l^–1 decreased pollen germination without affecting the formation of deformed pollen grains. Plants of the second group showed a higher rate of pollen germination under long than under short days. GA₃ at 200 mg l^–1 decreased pollen germination under either short- or long-day conditions compared with the controls but doubled the percentage of deformed pollen only under short days. Stamens in control plants grew four times as long under long- than short-day conditions. GA₃ did not affect stamen length under long days but significantly enhanced their growth under short days.     

Yields and the extent and causes of damage in cauliflower,bulb onion,and carrot grown under organic or conventional regimes

Summary

The effects of organic vs. conventional growing practices on yield, pest attacks, N uptake, and NO₃^– contents of three vegetable crops were examined. A range of cultivars of cauliflower (Brassica oleracea L. cv. Botrytis), bulb onion (Allium cepa L.), and carrot (Daucus carota L.) were grown organically and conventionally in a sandy-loam soil. Ranking of cultivars according to yield and susceptibility towards insect attack and fungal disease was similar in the two systems. Yields of cauliflower and onion were 20% and 45% higher, respectively, when grown conventionally. No differences in carrot yields and discard rates were observed between the two systems. Generally, the reasons for discarding varied between the two systems. In organically grown cauliflower, damage by slugs was the main reason for discarding, with 9% discarded, while hollow stem was more prevalent in conventionally grown cauliflowers, where 7% was discarded. No statistically significant differences were found between discard rates or causes in bulb onions grown organically or conventionally. Conventionally grown carrots were significantly more damaged by carrot root fly with 5% of carrots discarded, even though the flies were also present in the organic system. In contrast, more carrots with morphological defects were seen in the organic system, where 29% were discarded. The lower yields in organically grown vegetables can be explained mainly by the management practices specific to the organic system that are designed to facilitate weed and pest management. In addition, inadequate early nutrient supply provides a possible explanation for the lower yields in organically grown cauliflowers and onions, as well as the lower planting density of onions.     

Morphology and anatomy of pollen grains from male-fertile and male-sterile cultivars of chestnut (Castanea sativa Mill.)

Summary

Pollen morphology and ultrastructure are described for four male-fertile cultivars (‘Firdola’, ‘Karamehmet’, ‘Sar?a?lama’, and ‘Hac?ömer’) and two male-sterile cultivars (‘Osmanog?lu’ and ‘Vakit Kestanesi’) of chestnut (Castanea sativa Mill.) using light microscopy and both scanning and transmission electron microscopy. Pollen grains of both male-fertile and male-sterile chestnut cultivars are tricolporate, the germinal furrow extending almost the full length of the grain axis. Pollen grains have a slightly reticulate exine. Pollen grain length varied from 13.33 – 21.30 µm, and decreased significantly in the male-sterile cultivars. Three different pollen shapes were observed among the cultivars: prolate, perprolate, and sub-prolate. The ultrastructure of the pollen grains did not differ between male-fertile and male-sterile cultivars. Intine, exine and total wall thickness (exine + intine) of pollen grains were determined as: 83.2 – 153.1 nm, 432.8 – 520.0 nm, and 516.0 – 651.6 nm, respectively; and variations were significant (P ≤ 0.05) among cultivars. The percentages of in vitro germination of pollen grains of male-fertile cultivars were between 11 – 78%, and the variations among cultivars were significant (P ≤ 0.05). The percentages of empty pollen grains observed among cultivars ranged from 3 – 32%. The correlation coefficient between the percentage of normal pollen and the germination rate was r = 0.898 (P ≤ 0.01).     

Diversity of S-RNase genes and S-haplotypes in Japanese plum (Prunus salicina Lindl.)

Summary

This report demonstrates the diversity of S-haplotypes in Japanese plum by molecular cloning of genomic DNAs and cDNAs that encode S-RNases. Nine different DNA fragments, designated as S^a–Sⁱ, were obtained from 17 Japanese plum cultivars by PCR with an S-RNase gene-specific primer set, Pru-C2 and PCE-R. Eleven different S-haplotypes were found in these cultivars. The banding patterns obtained with another S-RNase gene-specific primer set, Pru-T2 and PCE-R, corresponded to the S-haplotypes predicted from the Pru-C2 and PCE-R primer set. Several cultivars had the same S-haplotypes. Partial genomic DNAs for eight S-RNase genes and cDNAs for two S-RNases were cloned and sequenced. Deduced amino acid sequences contained conserved regions among the rosaceous S-RNases. Comparisons of the sequences from cDNAs and genomic DNAs revealed the presence of two introns in the S-RNase genes of Japanese plum as in other Prunus S-RNase genes. Pollination incompatibility groups and self-compatibility in Japanese plum were discussed with reference to the S-haplotypes.     

Performance of some apple cultivars under tropical Zambian conditions

Summary

Ten apple cultivars (Malus domestica Bork) Ein Shemer, Anna, Rome Beauty, Tropical Beauty, Alexander, Orleans, Winter Banana, Black John, Starking Delicious and Red Delicious were evaluated for their suitability for tropical Zambian conditions. Winter Banana, Black John, Starking Delicious and Red Delicious, which were mostly high-chill cultivars, showed poor vegetative development: delayed budbreak, shoot growth and progressive loss of vigour and most of the trees died before maturity. Of the remaining low-chill cultivars, ‘Ein Shemer’ had the highest fruit yield at 49 6 2.3 kg tree²¹ and ‘Alexander’ the lowest (5.3 6 1.0 kg tree²¹). This response was due to the high number of fruits per tree, ‘Ein Shemer’ had up to 907 6 83.7 per tree whereas low yielding cultivars like ‘Rome Beauty’ and ‘Tropical Beauty’ had fewer than 106 6 25.3 fruits per tree. The individual fruit weight was inversely related to the total number of fruits per tree. It ranged from 58 6 5.1 g in Ein Shemer to 191 6 24.8 g in ‘Rome Beauty’.     

Meristem culture and micropropagation of a variety of ginger (Zingiber officinale Rosc.) with a high yield of oleoresin

Summary

Meristems of ginger with or without leaf primordia were induced to form shoots on three-quarter strength Murashige-Skoog’s (MS) medium containing sucrose 6%, coconut milk (CM) 20%, ascorbic acid (AA) 100 mg l^?1, glutamine (GL) 400 mg l^?1, activated charcoal (AC) 250 mg l^?1, 6-benzylaminopurine (BAP) 0.5 mg l^?1, indolebutyric acid (IBA) 0.4 mg l^?1 and agar 0.8%. Meristem-derived shoots exhibited consistent multiplication on three-quarter strength MS medium containing sucrose (3%), AA (100 mg l^?1), AC (100 mg l^?1), BAP (4–5 mg l^?1) and agar (0.8%). Liquid media (agitated or static) were less effective than a solid (agar-gelled) medium for micropropagation. Kinetin and naphthalene acetic acid (NAA) incorporated at various levels (0.01–0.8 mg l^?1) with or without added BAP and IBA neither improved plantlet formation nor enhanced shoot multiplication. The in vitro plants were successfully established in vivo and the rhizome yield was comparable with that of plants grown by conventional methods.     

Metabolite profiling reveals the involvement of aberrant metabolic changes in Gentiana triflora seed showing poor germination

Gentians are alpine plants and two endemic species, Gentiana triflora and G. scabra, are cultivated as ornamentals in Japan. Because most of the Japanese cultivars are F₁ hybrids, seed germination rate is an important factor for maintaining these cultivars. However, germination rates frequently differ among cultivars. Poor germination is a severe problem for gentian production, although there is almost no difference in their germination period and growth rate. In this study, we compared seed germination rates among three cultivars of G. triflora. A high rate of seed germination was observed in ‘Majel’ (MJ) and ‘Iwate’ (IW), but a low rate was recorded in ‘Iwate-Yumeminori’ (YM). We conducted a targeted metabolome analysis using these cultivars to elucidate the potential cause of inhibited seed germination. Multivariate analysis revealed that the aberrant accumulation of specific amino acids and a decrease in energy metabolites were observed in YM seed. Furthermore, protein concentrations and proteolytic activities in YM seed were lower than in MJ seed. These results imply that energy depletion was the main reason for the decreased rate of germination and that this depletion inhibited processes involved in seed germination, including de novo synthesis of the proteins necessary for germination.     

In vitro induction of chromosome-doubling in cultured shoots of three cultivars of mint (Mentha canadensis L.) treated with colchicine

Summary

To improve the yield and quality of essential oils, chromosome-doubling in mint cultivars was induced by treating shoots with colchicine in vitro. Shoot tips of three mint cultivars (‘68-7’, ‘73-8’, and ‘HU 39’) were cultured in vitro and treated at 2 months using either of two methods to induce chromosome-doubling. Explants were immersed separately in each of three concentrations of colchicine [0.1, 0.2, or 0.3% (w/v)] for 24 h or 48 h. Alternatively, shoots were cultured on solid 1.0× MS (Murashige and Skoog) medium supplemented with one of five concentrations of colchicine (10, 20, 30, 40,, or 50 mg l^–1) for 30 d. After each treatment, ploidy levels were measured by flow cytometry. The results showed that high yields of 4n plants were induced by the immersion of shoots in 0.2% (w/v) colchicine for 24 h (13.3%), or by culturing shoots on MS medium containing 20 mg l^–1 colchicine for 30 d (17.3%). The immersion method, which gave a survival rate of 93.3%, was more convenient and less phytotoxic to produce 4n mint plants. Compared with untreated plants, we observed fewer but larger stomata in chromosome-doubled plants. We also observed significant differences in the size, internode length, leaf length, leaf width, and stem width in chromosome-doubled mint plants.     

Effects of grafting height of MM106 rootstock on growth,lateral shoot formation and yield in apple trees

Summary

Between 2004 and 2008, the effects of different grafting heights on sylleptic shoots were tested in the apple (Malus domestica Borkh.) cultivars ‘Granny Smith’ and ‘Gloster’, and cumulative fruit yields were evaluated. MM106 apple rootstocks were grafted 10, 20, 40, or 60 cm above soil level in August 2004. The results showed that an increased grafting height significantly decreased tree height in both cultivars. The tallest and shortest trees were observed at grafting heights of 10 cm (153.0 and 170.0 cm) and 60 cm (141.3 and 143.5 cm) in ‘Granny Smith’ and ‘Gloster’, respectively.Among the various grafting heights tested, 60 cm in ‘Granny Smith’ and 20 cm in ‘Gloster’ gave the largest stem diameters (17.6 mm and 16.8 mm, respectively). The number of lateral shoots increased significantly with increased grafting height in both cultivars. The largest numbers of lateral shoots in ‘Granny Smith’ (10.75) and ‘Gloster’ (2.00) were obtained from a grafting height of 60 cm, while 2.55 and zero lateral shoots occurred at 10 cm grafting height in ‘Granny Smith’ and ‘Gloster’, respectively. Shoot lengths decreased significantly by increasing the grafting height. Grafting heights of 10 cm and 60 cm resulted in the tallest and shortest shoots in both cultivars. Cumulative fruit yields were significantly affected by grafting height in both cultivars. The highest yield was found for a 60 cm grafting height in both ‘Granny Smith’ (11.295 kg tree^–1) and ‘Gloster’ (4.818 kg tree^–1).The results of this study suggest that grafting heights of 40 cm and 60 cm have the potential to promote branching and early bearing for apple fruit production in sustainable and organic agricultural systems.